### 2 

## Recent History

EFED last reviewed (11/12/2009, DP Barcode D346169) the environmental issues regarding spray drift in a response to public comments on propos ed mitigation measures from the sulfometuron methyl Reregistration El igibility Decision (RED). 1



## Summary of Registrant Conclusions and Proposal

Our review has in view the Rights of Way (R OW) applications for which the registrant and stakeholders have previously requested be tter representation of current prevailing practices with regards to spray drift mitigation label language, in cluding buffers to minimize
off-site environmental risk. This review is intended to primarily address issues with regards to ROW applications although the low dri ft technologies discuss ed below are generally applicable to other product uses. The si ngle “swath” adjustments discussed below, however, generally only apply to ROW uses (and even these uses cannot uniformly be assured to be single swath either 2 

### . The single / reduced swat h number adjustment may be applicable to other specializ ed applications (such as s pot treatments with hand-held equipment). EFED modeling to test the effect of these factors on drift is documented in the Appendix to this review.

(1.) Registrant conclusions: Modeling with AgDRIFT® to simulate a singl e swath application shows that deposition, and consequently risk quotients, will be reduced by 50% rela tive to multiple swath applications.

EPA Response: We generally concur with this conclusion. Single pass / swath applications can be simulated with AgDRIFT 2.01 and we were able to reproduce the regist rant’s single swath results for Tier 2 AgDRIFT aerial applications (including those with ultra coarse drift profiles within AgDRIFT – see our Table 3 and also Tables 2, 3, and 4 in MRID 482619-01) and Tier 1 ground applications (s ee our Tables 1 and 3 and regi strant’s Table 5 and 6).

This has implications for rights of way uses of sulfometuron which are applied to areas which are likely covered in less than twenty swaths (a default assumption for both aerial and ground application analysis in AgDRIFT). So me re-evaluation of the previous buffer zones may be appropriate given many applic ations (forestry uses excluded) of sulfometuron methyl likely involve substant ially less than twenty sw aths. Although single

a 1 Relevant documents can be accessed through: http://www.epa.gov/opp00001/reregistration/sulfometuron_methyl/ or

at: http://www.regulations.gov/s earch/Regs/home.html#docketD etail?R=EPA-HQ -OPP-2008-0129 The RED is specifically available at: http://www.epa.gov/opp00001/reregistration/REDs/sulfometuron_methyl_red.pdf

2 Email dated 2/22/2011 from Jim A. Gray (Pesticide Feed and Fertilizer Director, North Dakota Dept. of Agriculture, Bismarck, ND) to Jim Roelofs, Govt. and International Services Br., Fiel d and External Affairs Div., OPP).

### 3 swath applications cannot be confirmed to be uniformly appropriate for even ROW applications, these types of applications likel y will normally involve fewer than 5 swaths.

With Tier 1 Ground Application assumptions in AgDRIFT, at 20 feet downwind from the treated area the predicted reducti on drift from a five swath application versus a 10 or more swath application is minimal at all dist ances downwind from the treated area ( Table 1 ). Use of a single swath (not practica l for all rights of way applicati ons) results in a 30% or more
reduction in drift at distances of 20 or more feet downwind ( Table 1 ). Similar reductions were obtained going from 20 to 1 swath (MRID 482519-01, Table 5).

Table 1. Effect of a reduction in the number of swat hs on drift from ground application (AgDRIFT Tier 1).

Distance

downwind 1 vs. 10

Swaths

% Reduction 5 vs. 10

Swaths

% Reduction 1 swath %

Drift 5 swaths %

Drift 10 Swaths %

Drift

10 feet 13.64% 2.27% 3.80% 4.30% 4.40%

20 feet 30.00% 5.00% 1.40% 1.90% 2.00%

72 feet 60.00% 0.00% 0.20% 0.50% 0.50%

Using 50 percentile Tier 1 data and a 4.17 foot application height. Refer to MRID 482519-01, page 21 for more details. Derived from Table 6 in MRID 482519-01.



### (2.) Registrant conclusions:
Further reductions in drift fr om aerial applications can be model ed for low drift technologies using nozzles producing extremely coarse and ul tra coarse droplet distributions in high spray volume, low speed applications by helicopt er. With the latter lo w drift conditions, offsite deposition is negligible, and buffers are not required to obtai n a level of protection for non-target aquatic and terrestrial plants that is equivalent to EPA's target values (Keigwin, 2009)

.

EFED Response: Clearly the new application technologies can reduc e drift substantially although more data and/or model development and va lidation are needed to fully c onfirm the effectiveness of these new technologies in actual practice. The EFED reviewed some of the secondary options available in AgDRIFT 2.01 Tier 2 aer ial application mode whic h include application equipment and method scenarios that reduce drift beyond those available in the standard Tier 2 options. Specifically, EFED evaluat ed the Accu-Flo 028 nozzle drift predictions 3

3 The model predictions discussed here are from specific Spray Drift Taskforce (SDTF) experiments which were used in the development of the empirical model AgDRIFT; these datasets are made available in AgDRIFT for the estimation of drift under specific applica tion scenarios. Note that while these da ta are vetted and accepted for support of EFED’s spray drift models, this does not necessarily translate into a specific datase t with a specific nozzle type as being representative of current technology in use for a specific pesticide / use site combination.

### 4 with AgDRIFT 2.01 and obtained near ly identical results to those presented in the registrant’s submission (which used the sa me input parameters fo r AgDRIFT 2.0.09). We also tested the Accu-Flo 047 dataset in AgDRI FT (also delivering ultra coarse droplet size spectra when applied at a speed of 40 mph or 60 mph) and f ound similar drift reductions from the use of this equipment.

(3.) Registrant Conclusions: The limitations in the AgDRIFT® ground model can be overcome by consideration of the underlying experimental data and by supplem enting the SDTF data with results of the
Canadian Drift Model. Data from the SDTF shows that the AgDRIFT® model overestimates drift from the extremely coar se nozzles used in turf and ROW applications.

EFED Response: Unfortunately, we are not able to validate the Canadian data and models for direct use to estimate exposure from uses in the USA at this time. In the regist rant’s submission, the Canadian drift model is in parti cular a primary source of drift estimations for the low drift technologies in ground applicatio ns. OPP / EFED needs further validation of the level of drift reduction obtainable with these technologie s in ground application. While we consider the Canadian data submitted by t he registrant suggestive of t he level of mitigation that might be achievable with the newer drift reduction technologies, we cannot yet rely on this
data because it has not been validated for use wit hin OPP. However, as also discussed in the registrant’s submission, with the underlying data used for AgDRIFT ground spray drift predictions there is some limited verification of the level of drift reduction obtainable with technology delivering extremely course to ul tra course droplet spectra (utilizing “8010LP” nozzles). The 8010LP data are not cu rrently accessible through AgDRIFT 4 

### but are available in a report submitted to EPA (MRID 43508001, SDTF Study I94-001). Drift reduction relative to comparable Tier 1 Ag DRIFT runs was about 32 to 86% at 25 to 75 feet from the treated area ( Table 2 ).

Table 2. Comparison of standard Tier 1 ground applica tion predicted drift with drift from nozzles delivering extremely course droplet spectra.
(Boom Height = 1.67 feet) (Boom Height = 4.17 feet)

Drift

Measured

at: 

### %
reduction
w/ 8010LP Tier 1

% drift 8010LP %

drift 

### %
reduction
w/ 8010LP Tier 1

% drift 8010LP %

drift

25 feet

downwind 

### 84.31% 1.02% 0.16% 

### 32.75% 1.71% 1.15%

75 feet

downwind 

### 85.71% 0.35% 0.05% 

### 45.61% 0.57% 0.31%
Comparison of the SDTF data with the 8010 LP nozzle (VMD = 762 um) with the AgDRIFT Tier 1 scenario (VMD = 341 um) for both low and high boom applications. 90 th Percentile curves all at 4 swaths (See MRID,
48251901, p. 22, Table 7).

4 The AgDRIFT user interface for ground applications currently only includes the Tier 1 module with very limited user options; if and when a Tier 2 option for

### 5 (4.) Registrant Conclusions: Considering the difference between the mode l and the experimental data, the buffer
distance can be reduced to 5 ft for low boom (hand held) spra yers and 10ft for high boom ground sprayers to obtain RQs equivalent to those calculated for the multiple swath application and fine to medium/coarse DSD us ed as the basis for EPA's buffer proposal.
The Canadian drift model demonstrates that applications with low boom, extremely coarse nozzles will produce lower off-target deposit ion than predicted by the AgDRIFT® model. The same level of protection targeted by EPA at 30 ft for spot applications with hand-held sprayer applications can be obtained at 3 ft using deposition from the experimental trials or with the Canadian model for extremely coar se nozzles. For high boom applications with coarse or very coarse nozzles, the Canadian model predicts deposition similar to the EPA target values at 10-15 ft.

EFED Response: As noted above, we are unable to verify th e representativeness of the Canadian drift model for use in US pesticide regulation. Other evidence from data used to develop approved EFED models does show that some significant reductions are available with equipment set to deliver courser spray s pectra and with a reduced number of swaths.

The analysis of specific data sets (as discuss ed above in this review) does show that there is potential for significant reductions in spra y drift with the use of nozzles and application methods that deliver extremely course or ultra course droplet spectra. Based on the AgDRIFT modeling scenario s presented below in Table 1

, Table 2 , and Table 3 , we cannot confirm the registrant’s conclu sion that 5 ft and 10 ft buffers for ground applications of sulfometuron would be adequately pr otective of non-target plant species. These data do show that if applications are made deliverin g extremely course dr oplet spectra a modest
reduction in buffers could be made while al so obtaining exposure reductions. As an example, at a boom height of 1.67 spray drif t from ground applications could be reduced from 0.35 to 0.16 % while reducing a buffer from 75 to 25 feet ( Table 2 ). EFED is not in a position to determine, however, whether such equipment is being routinely used to the exclusion of equipment deliv ering finer droplets and under environmental allowing more
drift to occur.



## ANALYSIS

A selected summary of our analysis to validate the registrant’s submission (using options available in AgDRIFT is provided in Table 3 , additional modelin g documentation is provided in the Appendix to this review. No te that additional analysis was previously provided in DP Barcode D346169 (“Response to Environmental Fate and Effects related
Comments on Sulfometuron Rer egistration Eligibility Do cument”, dated 11/12/2009).
We were unable to validate at this ti me the Canadian model based analysis by the registrant (MRID 4826519-01, Tables 7, 8, 9, and 11 and Figures 1 to 3). Nonetheless, the

### 6 data validated for AgDRIFT suggests that ther e can be (for example) a 90% reduction in drift from aerial applications at 50 feet with use of select ed equipment. (Compare Run ID 2
with Run 11a/11b in Table 3 .)

The amount of drift from the bes t nozzles for aerial applications is even lower than the drift estimated with single swath ground applicat ions (representing some Rights of Way applications) using currently available Tier 1 options in AgDRIFT (Run ID D6-1 and D6-3) 5



### .

For drift from ground applicati ons at about 25 to 75 feet, approximately 30 to 90% reductions (compared to application met hods and conditions normally assumed in AgDRIFT Tier 1) may be possible with fewer sw aths (4 is a reasonable maximum expected number for most uses) and use of equipment app lied to deliver extrem ely course droplet spectra. The amount of reduction is hi ghly dependent on boom height with the best percentage reductions obtained with a lower boom height ( Table 2 ).

Table 3. Comparison of previous aerial modeling to some of the best drift reduction options currently available in AgDRIFT fo r aerial or ground applications.

DISTANCE
DOWN WIND (FEET) MODE:
AERIAL

TIER II MODE:
AERIAL

TIER II MODE:
AERIAL

TIER II MODE:
GROUND

TIER I MODE: GROUND

TIER I

Lbs ai/A [% of rate] Lbs ai/A [% of rate] Lbs ai/A [% of rate] Lbs ai/A [% of rate] Lbs ai/A [% of rate]

0 0.0769 [27.34] 0.1124 [40.0] 0.1124 [40.0] 0.2834 [100.8] 0.2810 [100.0]

7 NC 0.0127 [4.52] 0.0134 [4.78] 0.0180 [6.40] 0.0200 or 0.0170 (EPA) [7.10]

13 NC 0.0026 [0.94] 0.0024 [0.87] 0.009 [3.20] 0.0071 or 0.0073 (EPA) [2.50]

15 NC NC NC NC 0.0060 [2.2]

20 NC 0.0008 [.0.27] 0.0008 [0.275] 0.0057 [2.00] 0.0040 [1.40]

26 NC 0.0004 [0.16] 0.0004 [0.15] 0.0042 [1.50] 0.0027 [0.90]

50 or 52 0.019 [6.77] 0.0002 [0.09] 0.0002 [0.08] 0.0010 [0.30] 0.0020 [0.70]

72 or 75 0.0127 [4.52] 0.0002 [0.09] 0.0003 [0.10] 0.0015 [0.50] 0.0006 [0.20]

100 0.0091 [3.23] NC NC NC NC

125 NC 0.0000 [0.0001] 0.0000 [0.0001] NC NC

200 0.0039 [1.39] 0 0 NC NC

500 0.0016 [0.59] 0 0 NC NC

5 Note, however, that if coarser nozzle da ta could be selected for ground applica tions then the drift estimates would be lower as represented in 

### Table 2

.

### 7 750 0.0012 [0.44] 0 0 NC NC

900 0.0011 [0.39] 0 0 NC NC

Run ID 1 2 11a (EPA) 11b (DuPont) D6-3 (DuPont) D6-1 (DuPont)

Key Input Assumptions 1

Applic. Rate, lb
ai / A 0.281 0.281 0.281 0.281 0.281

Wind Speed, mph 10 10 10 10? 3 10? 3

Application height, ft. 10 10 10 4.17 2 4.17 2

Nozzle set info NA Accufl o 028 Accuflo 028 NA NA

Median Droplet Size (um) 384 1213 1213 341 341

Drop size
distribution Coarse (ASAE) Very to extremely

coarse (ASAE) -
Now Ultra

Coarse Very to extremely

coarse (ASAE) -
Now Ultra

Coarse Fine to
medium coarse (ASAE) Fine to medium coarse (ASAE)

# of Flight lines (Swaths) 20 1 1 10 1

Data Percentile NA NA NA 50 50

Spray Volume, gal/ A 10 10 10 NA NA

Application Equipment WASP Helicopter WASP Helicopter WASP Helicopter Ground Ground

1 Run #2 is repeated from the previous REVIEW by EFED; Runs 11a and 11b represent the registrant’s choice (see MRID 48261901) of an aerial application equipment / method option in AgDRIFT said to represent the better types of appli cation methods currently in use. Note that these are single swath scenarios and therefore the re sults only apply to single pass rights of way applications. Runs D6-3 and D6-1 represent the best options to minimize drift from ground applications that are currently available in Ag DRIFT (including examination of the impact of reducing the number of swaths to better represent most rights of way applications.)

2 Select the “high boom” option for AgDRIFT ground application model input.

3 Believed to be on average about 10 mph, but this is not specified in the AgDRIFT model documentation. The Tier 1 data likely reflect data coll ected at a wind speed of about 10 m ph as this is generally the default assumption used by AgDRIFT.

### 8 

## APPENDIX

Sample Input and Output Data: AgDRIFT A ccuflo 028 Nozzles, Rights of Way application

Figure 1. Input and Drift at 50 feet for Accuflo 028 ROW application (50 ft).

Figure 2. . Input and Drift at 50 feet for Accuflo 028 ROW application (15 ft).

### 9 Figure 3. Droplet distribution input for AgDRIFT: Accu-Flo 028 nozzles.

### 10 Figure 4. Accu-Flo 028 nozzle specifications.

### 11 Figure 5. Input screen and sample outp ut for Accu-flo 04 7 nozzle, 40 mph application (for comparison to the Accu-flo 028 run).

Figure 6. Droplet size spectrum fo r SDTF Accuflo 028 equipment.



### ***************************************

### 12 Figure 7. AgDRIFT input and sample output screen: Ground application, Tier 1, high boom, single swath (comparable to the right side of Table 5 in registrant submissions (MRID 482519-01).

### 13

### 14 Figure 8. AgDRIFT Tier 1 Ground Application single swath (compare with MRID 48251901, Table 6 – column 1).